Well, like others have said there is no right answer, but I would say for beginners Unity is easier to get started with. In UE4 you need to learn to use C++, and it has a crap ton of other editors to learn. It has blueprints, which, depending on your programming experience, may be easier than scripting in Unity, but if you are planning on making a full first person action your going to need to learn more complicated C++ stuff anyway. UE4 looks prettier though, especially compared to the Unity free version. Unity 5 is coming out soon, which should increase the graphical fidelity.

Don't you have to pay extra for a Unity mobile license also, $1500, and you also need the pro version, $1500, before you can buy a mobile license?

Don't you have to pay extra for a Unity mobile license also, $1500, and you also need the pro version, $1500, before you can buy a mobile license?

Overall UE4 is a better deal price wise and tech wise it has almost all the features plus it has an excellent visual scripting editor(Blueprints). Unity's selling point is it's assest store and huge amount of community support/knowledge. But as said if you can get Unity store assests in FBX format or are able to convert other formats to FBX then maybe UE4 is the better option.

Obviously the other consideration is scaleability, whether UE4 can build the type of game you want.

well, there ARE basic versions of the mobile licenses, which originally were around 400$ per target platform.

Unity changed its pricing some time ago (when some features, like hard shadows, moved to the free version)... by that time, the basic mobile licenses became free too. So as long as you do not need Pro features, you can build for iOS and Android and not pay anything.

But this is an additional thing to keep in mind: If you do need pro features, and want to target both iOS and Android (Windows Phone and Blackberry Pro seem to be included in the standart Pro license), the Price per seat goes up to 4500$ initially... which to my mind is MUCH harder to swallow than the initial Price for Windows/Linux/MacOS building capability of 1500$.

Same for the consoles, though consoles traditionally meant additional costs for "entry".... no idea if this has gone out of the window with Sonys and Microsofts newfound love for Indies though.

Personally I wouldn't worry about what you call scalability. If you look at what was built with the Indie version of Unreal3, UDK, it was used to build almost every genre of games...

I am pretty sure UE4 is just as versatile.

How easy it is to build an RTS bvs. building the same in Unity, no idea. YMMV anyway as some people might find one toolset or the other more intuitive, or expect more or less handholding by the engine.

The ONLY thing I would be skeptical about, is wheter UE4 is as good as Unity as an engine for 2D games. Though that is, to me, also borderline, using a fully fledged 3D engine for 2D development might give you more mileage out of your Unity license, but is certainly overkill in many situations. But that is again subjective.

It might be a good idea to try both of them out before making a decision. Unreal is only $20, and there's a free version of Unity.

Design a small scene with a couple of lights and a few physics objects etc, and try to build the same thing in each editor. That should provide at least a feel for how each engine is put together.

Absolutely... do that before you have written tousand lines of code and sunk many $ into additional assets like I have done on my current project in Unity.

I though about switching over to UE4 the whole year, in the end I rather wanted to keep up momentum and finish a prototype in Unity before I devote the time to learn a new engine... and by doing that, I would give Unity 5 a chance to show some promise.